A prodigious spinner where his winter habitation is concerned, the caterpillar finds his glands exhausted and is reduced to the strictly necessary amount when the time comes for making the cocoon. Too poor in silk, he strengthens his flimsy cell with a facing of earth. With him it is not the industry of the Bembex [22], who inserts grains of sand in her silky web and makes a solid casket of the whole; it is a summary sort of art, devoid of delicacy, which just casually sticks together the surrounding earthy refuse. Moreover, if circumstances demand it, the Pine Caterpillar can do without earth. In the very midst of the nest I have sometimes—very rarely, it is true—discovered cocoons which were perfectly clean. Not a scrap of alien matter defiled their fine white silk. I have obtained similar specimens by placing caterpillars under a bell-glass in a pan provided only with a few pine-twigs. Better still: an entire procession, a good-sized one too, gathered at the opportune moment and enclosed in a large box containing no sand nor any material whatever, spun its cocoons with no other support than the bare walls. These exceptions, provoked by circumstances in which the caterpillar is not free to act according to his wont, does not in any way invalidate the rule. To prepare for the transformation, the Processionary buries himself, to the depth of nine inches and more, if the soil permit. Here a curious problem forces itself upon the observer’s mind. How does the Moth contrive to ascend from the catacombs into which the caterpillar has descended? Not in the finery of her perfect state—the big wings with their delicate scales, the sweeping antenna-plumes—dare she brave the asperities of the soil, or she would issue thence all tattered, rumpled and unrecognizable. And this is not the case: far from it. Moreover, what means can she employ, she so feeble, to break the crust of earth into which the original dust will have turned after the slightest of showers? The Moth appears at the end of July or in August. The burial took place in March. Rain must have fallen during this lapse of time, rain which beats down the soil, cements it and leaves it to harden once evaporation has set in. Never could a Moth, unless attired and equipped with tools for the purpose, break her way through such an obstacle. She would perforce require a boring-tool and a costume of extreme simplicity. Guided by these considerations, I institute a few experiments which will give me the key to the riddle.